This invention relates generally to the measurement of very thin dielectric films adhering to a substrate material and more particularly to a measuring system which measures the variation in a polarized light beam caused by the influence of the thickness of an adhering thin film in relation to the Brewster angle of the substrate material.
Systems presently exist that are capable of measuring the depth of films having a thickness of approximately two hundred Angstroms and greater. Nanometrics Incorporated of Sunnyvale, Calif., has developed measuring equipment such as its NanoSpec Automatic Film Thickness (AFT) system and various manufacturers produce the well known ellipsometer. These two systems are suitable for determining the thickness of thicker films. Ellipsometers are capable of measuring very thin films down to about 10 Angstroms, but such ellipsometers are very costly, the process is very slow, and very complex mathematics are involved. The stringent specifications of the present day electronic industry require reasonably priced instruments that will rapidly and accurately measure film thicknesses down to about 20 Angstroms. This need has remained unsatisfied until the conception of the invention described herein.